WWU -- Chemistry Experiment 56: Synthesis of an Ester from an Alcohol and Carboxylic Acid Structure determination by Infrared Spectroscopy

WWU -- Chemistry Infrared Spectroscopy Read Chapter 25, pp 833 to 867 Work problems on page

WWU -- Chemistry Typical Infrared Absorption Regions

WWU -- Chemistry O-H stretch The OH peak is very strong and broad! It usually appears near 3400 cm -1

WWU -- Chemistry C-H stretch sp 3 C-H stretch comes at 2950 cm -1 sp 2 C-H stretch comes at 3050 cm -1 sp C-H stretch comes at 3300 cm -1

WWU -- Chemistry C=C stretch C=C stretch occurs near 1650 cm -1 It is often weak unless it is conjugated to a C=O

WWU -- Chemistry Normal Base Values for C=O Stretching

WWU -- Chemistry C-O stretch The C-O band appears in the range of 1300 to 1000 cm -1 Look for one or more strong bands appearing in this range! Ethers, alcohols, esters and carboxylic acids have C-O bands

WWU -- Chemistry C-H bendings Bendings aren’t as important as stretches. See page CH 2 bending: 1450 cm -1 CH 3 bending: 1375 cm -1

WWU -- Chemistry Cyclohexanol O-H stretch bending C-O stretch sp 3 C-H stretch

WWU -- Chemistry Ethyl Butanoate sp 3 C-H C=O stretch C-O stretch

WWU -- Chemistry 4-Methyl-2-pentanone C-H < 3000, 1715 cm -1 C-H stretch C=O stretch

WWU -- Chemistry 4-Methyl-3-penten-2-one C-H stretch C=O stretch C=C stretch

WWU -- Chemistry Experiment 15 Spearmint and Caraway Experiment 15, pp Essay: pp Technique 25 (Infrared spectroscopy) Technique 22 (Gas Chromatography, especially, Section 22.8 on page 806 and Fig 22.7) Technique 23 (Polarimetry)

WWU -- Chemistry Spearmint and Caraway Oils Limonene is present In both oils

WWU -- Chemistry The experiment Run the IR spectrum on the two enantiomers Run a sample of each enantiomer through the gas chromatograph Determine the optical rotations for each enantiomer Calculate the specific rotation for each enantiomer

WWU -- Chemistry Nucleophilic Substitution: Competing Nucleophiles Experiment 21

WWU -- Chemistry Reading Assignment pp (Exp 21) and (exp 58) Chapter 10 in your lecture textbook Review Techniques 1 through 6 Technique 7 (Sections 7.2, 7.4, 7.5, 7.8) Technique 12 (Sections 12.5, 12.9, 12.11) Technique 22 Technique 21 (omit this quarter)

WWU -- Chemistry Changes to Exp 19 laboratory We will be using 1-pentanol, 2-pentanol, 3-pentanol and 2-methyl-2- butanol instead of what is shown in the book. The procedure stays the same; just change the alcohols. Start 21A first, then do 21B, and then come back to finish 21A. Part 21C: gas chromatography only Signup for 1, 2, and 3-pentanol

WWU -- Chemistry The S N 2 Mechanism

WWU -- Chemistry The S N 1 Mechanism 1935: Hughes & Ingold carbocation

WWU -- Chemistry Assisted S N 2: Mechanism

WWU -- Chemistry Assisted S N 1: Mechanism

WWU -- Chemistry

Gas Chromatography Results: 1-Chloro pentane and 1-Bromopentane R-Cl R-Br solvent

WWU -- Chemistry Ret. Time Width Peak Peak Result Time Offset Area Sep. 1/2 Status No. Name () (min) (min) (counts) Code (sec) Codes BB BB ========== ======= ========== Totals: Total Identified Counts associated with halides: counts Gas Chromatography Results: 1-Chloropentane and 1-Bromopentane from 1-pentanol Assume that all response factors = Round off the values to: 9.9 % 1-chloropentane 90.1 % 1-bromopentane Important! Other components may appear on the printout. If so, be sure to recalculate for only 1-chloro and 1-bromopentane! Make sure that the total equals 100%

WWU -- Chemistry Do the results of this experiment with 1-pentanol fit with what you expected?

WWU -- Chemistry Gas Chromatography Results: 2-Pentanol in the solvent nucleophile mixture solvent 2-chloropentane 3-chloropentane 2-bromopentane 3-bromopentane

WWU -- Chemistry Gas Chromatography Results: 2-Pentanol in the solvent nucleophile mixture Ret. Time Width Peak Peak Result Time Offset Area Sep. 1/2 Status No. Name () (min) (min) (counts) Code (sec) Codes BV VB BV VB ========== ======= ========== Totals: Total Identified Counts associated with halides: counts Round off the values to: 21.7 % 2-chloropentane 11.7 % 3-chloropentane 46.8 % 2-bromopentane 19.8 % 3-bromopentane Important! Other components may appear on the printout. If so, be sure to recalculate for only the four halides! Make sure that the total equals 100%

WWU -- Chemistry Why are we obtaining mixtures of halides in this reaction? Time for chalk!!

WWU -- Chemistry Gas Chromatography Results: 2-Methyl-2-butanol in the solvent nucleophile mixture solvent 2-chloro-2-methylbutane 2-bromo-2-methylbutane

WWU -- Chemistry Gas Chromatography Results: 2-Methyl-2-butanol in the solvent nucleophile mixture Ret. Time Width Peak Peak Result Time Offset Area Sep. 1/2 Status No. Name () (min) (min) (counts) Code (sec) Codes BB BB ========== ======= ========== Totals: Total Identified Counts for the two halides: counts Assume that all response factors = Important! Other components may appear on the printout. If so, be sure to recalculate for only the two halides! Make sure that the total equals 100% Round off the values 44.1 % 2-chloro-2-methylbutane 55.9 % 2-bromo-2-methylbutane

WWU -- Chemistry We expect that the reaction of 2-methyl-2-butanol with the solvent nucleophile mixture to be S N 1. Why didn’t it come out as a mixture? Life is never straightforward!

WWU -- Chemistry Important notice about next week’s lab lecture Friday, May 19 th Bond Hall 109 2:00 to 2:50

WWU -- Chemistry Important notice: Final Exam The exam will be held in SL 110 rather than SL 130 on Thursday, June 8 th 3:30-5:30